Drier



May 1, 1928.

H. C. HARVEY' DRIER 2 Sheets-Sheet 2 il July 20. l

Patented May 1, 1928.

UNITED STAT-ES 1,668,314 PATENT OFFICE.

HAROLD C. HARVEY, OF TRENTON, NEW JERSEY, ASSIGNOR T THE AGASOTE BOARD COMPANY, OF TRENTON, NEW JERSEY, A CORPORATION OF NEW JERSEY. i"

DRIER.

Application led July 20, 14926. Serial No.. 123,613.

This invention relatesv to drying apparatus, and more particularly to apparatus for drying sheet material, and has special reference to the drying of pulp board.

Pulp board is usually .made by running paper pulp, wood pulp, or the like, preferably with an admixture of a suitable binder into a mold, and by means of pressure removing the majority of the water (see, for

instance, U'.V S. Patents 971,936-1,272,566, and 1,506,509) and subsequently drying out the remainder of the water by the application of heat; preferably in a suitably constructed drier. While my drier may be employed in connection with the drying of various kinds of sheet material, for instance, 'plaster board or veneer, I shall describe it with special reference to its use in connection with the drying of pulp board, as this material has to be dried with particular care.,

The drying of pulp board should, if possible, be so conducted as to avoid, as far as possible, the setting up of strains within the material, which, when the board is subjected to adverse atmospheric influences, tend to warp the same. Heretofore it has, so far as I am aware, been the practice to dry the board as uniformly as possible, or to effect the drying first at two of the edges, working from such edges towards the center. When this method was employed, very great care had to be taken to avoid the formation of the interior strains hereinafter referred to. I have found that such strains can b e avoid-v tent, by drying the board along one of its central lines while holding Fit against warping, and then drying thematerial in each direction from the central lines towards the edges.

My improved drier is designed toy carry out this method. `In the drawings, Fig. 1 is aA plan view of one form of my improved drier with the roof removedito permit such parts to be visible as would be concealed by such roof. Fig. 2 is a vertical view of the drier'partl-yin section. Fig. 3 is a partial section along the lines 3 3 of Fig. 2,

and Fig. 4 is a right hand end view of Fig.

2. 1, 1 are the side walls forming with the roof 2 and the baffles hereinafter referred to,

the drying chamber 3. 4, 5 are motors operating fans 6 and 7 respectively for drawing air through conduits 8 and 9 respectively inthe directions indicated by the arrows in ed, either completely, or to a very great ex-l Fig. 2. Conduits 8 and 9 are connected with the manifold 10 adapted to receive a current of air from manifolds 11 and 12, each o y which is connected with conduits 13 provided with apertures 14, cooperating with apertures 15 in the walls 1 and 2 so that air may be drawn from the right hand of chamber 3 through apertures 15 and 14, conduits 13, manifolds 11, 12 and manifold 10, conduits 8 and 9, twofans 6 and 7. i

From these fans the air is blown through connections 16 and 17 respectively to manifolds 18 and 19 respectively. To the manifold 18 there are connected .a number of main air distributing lconduits 20, 20, through which the air is conducted to airs of branch pipes 21, 22, 23, 24, 25, 26, 2. and 28. The main air conduits and the branch pipesare each provided with perforations 29 at the upper and lower surfaces, with the exception of the uppermost conduit and its associated branch p1pes, which are perforated at the bottom only, and the lowermost conduit and associated pipes, which are perforated at the top only. l

The manifold 19 is connected witha main air conduit 30 having pairs of branch pipes 31, 32, 33, 34, 35, 36, 37 and v38, similar to main air conduit 20 and its associated branch pipes; except that the branch pipes are progressively shorter as they approach the point at which, as will hereinafter he shown, the sheets are introduced into the drier.

The material intake end to the drier' is provided with a hood 39 ending in an exgo haust stack 40,V the Vhood resting on vertical walls 41 and 42. l

The drier is provided with the usual conveying rollers 43 and heating pipes 44, as is usual in sheet driers of this particular type. In order not to obscure showing on the drawings unnecessarily, these conveyors and heating -pipes are indicated only. Four pairs of sets of rollers are provided in the apparatus shown in the drawin and these extend through the entire drylng chamber so that sheet material may be conveyed from one end to the other cf the apparatus.

The steam pipes are provided in association with the conveyors throughout all the drier, except the right hand, or cooling end thereof, designated as 3a. Bafiies 45 are provided at the intake end and at the end of the heating pipes adjacent the chamber 3a. These bailles do not interfere with the 119 les passage of the sheet material, but assist in preventing escape of the Iair, from the. drier, except through the stack 40.

In a general way, my apparatus, with the exception of the main air conduits 20 and 30 and their associated branch pipes, is very similar to the apparatus shown in United States Letters Patents to Coe, 1,000,376, dated August 15th, 1911 and to Collier and Vance, 1,447,836, dated March 6th, 1923; 1,508,924 dated September 16th, 1924, and 1,517 ,2- 5 dated November 25th, 1924, to which patents reference is made for details of the operating parts of my drier; such patents representing a drier of the type in extensive use in this country.

When it is desired to dry a sheet o' material by my apparatus, such sheet is drawn into the apparatus and passed through the same between the rollers 43 of the conveyor lying between two sets of main air conduits 20, 30 and their associated branch pipes, and steam is passed into and through pipes 44; all in the weltknown manner. s'shown in the illustrated example, the conduits 8 and 9 lead to air heaters 46 and 47 respectively, the latter in turn being connected respectively with the fans 6 and 7. rlhese heaters serve to preheat the air prior to its distribution by the fans 6 and 7 by which the air is blown through the main air conduits 20, 30 and their associated branch pipes into the interior of the drier. As the sheet passes between two of the main air conduits 20 and their associated branch pipes, it is subjected to the drying action, not only of the steam pipes 44, but of the hot air blown through apertures 29.

If the apparatus is properly proportioned :for the work to be done, the sheet, if made of wet pulp, will have approximately 68%.*

of its vmoisture removed when it reaches the space between two tiers of branch pipes 38; that is to say, the various portions of the sheet will have been reduced uniformly to this extent of moisture, as they reach such position. As the sheet passes onward beyond such position, it is still subjected to the drying action of the steam pipes 44; but only the central longitudinal portion is subjected to the drying action of the hot air passing through the apertures to the branch pipes 38. As the most intensive drying action is, therefore, at the center of the sheet, the-center will first be dry; the sheet drying progressivelyl towards the edges as it passes between the progressively longer tiers of branch pipes 37-31. `When it passes beyond the baes into the cooling chamber 3",

meas 14 it is completely dry; or at least dried to the desired, extent. As it passes through 'the cooling chamber 3, it gives u its heat rapidly to the air passing throng apertures l5 and associated manifolds and conduits to the interior of the drier in the manner hereinbeiore described.

A large proportion of the heat given ofi' by the material which it is desired to cool is thus reused in heating the fresh material which it is desired to dry.

When drying sheet material, the apparartus should be so proportioned that by the time* the portion of the board reaches the tiers of smallest branch pipes 38, its intercellular moisture should have been removed, so that the further drying operation drives od colloidal moisture. Colloidal moisture is such moisture as is absorbed by the fibre proper and is present therein even when it is in an air-dry condition, whereas intercellular moisture is such moisture as is present between the fibres.V l have found that strains and stresses within the dry sheet, which render the sheet liable to distortion when exposed to unfavorable atmospheric influences, can be avoided almost entirely, if not entirely, b conducting the drying operation, after Jllie intercellular moisture has been removed in such a manner as to remove the colloidal moisture iirst, from the' central lines of the sheet, and then progressively towards the edges.

I claim:

1. The method of drying a sheet of brous material which comprises drying such sheet until the intercellular moisture has been removed and then removing the colloidal moisture rst in the region immediately adjoining the central line thereof and then at uniformly progressive distances outward from` such line, substantially as and for the purpose described.

2. In an apparatus for-drying sheets of iibrous material the combination with a drying chamber of a conveyer for conveying a sheet of material through said chamber, a series of spraying conduits 'for spraying a heated drying medium in the form of independent jets upon said sheet, and a second series of spraying conduits for spraying a heated drying medium in the form of independent jets upon said sheet, the conduits of such second series increasing in length transversely of the sheet in progressive sequence in the direction of travel thereof.l

In testimony 'whereof l have hereunto set my hand.

HAROLD C. HARVEY. 

